1. Field of the Invention
Aspects of the present invention relate to a secondary battery, and more particularly, to a squeeze pin, and a secondary battery using the same, that improves the coupling intensity of an electrode tab and a lead terminal, prevents the damage of a protection circuit module, and reduces the cost.
2. Description of the Related Art
Portable electronic devices, such as mobile phones, camcorders, PDAs, and the like, have been actively developed and produced. Accordingly, users have increasingly demanded that the portable electronic devices should be light, small, and mobile. Specifically, to operate the portable electronic devices in the places where there are provided no sources of electricity, rechargeable secondary batteries having a high energy density as the source of electricity are used. Therefore, the power supply time, size, weight, and the like of the secondary batteries are considered as being very important in determining the portability and mobility of the portable electronic device.
Examples of secondary batteries include nickel zinc batteries, nickel cadmium batteries, nickel metal hydride batteries, lithium secondary batteries, and the like. Among these batteries, lithium secondary batteries having a high operating voltage and a high energy density per unit weight are widely used. A lithium secondary battery is made by sealing an electrode assembly and an electrolyte in an outer case formed of a material, such as aluminum and the like.
Lithium secondary batteries are classified as a cylinder type, a prismatic type, and a pouch type, depending on the shapes of the outer case. Further, lithium secondary batteries are classified as lithium ion batteries and lithium polymer batteries, depending on the electrolyte used therein.
A secondary battery includes a protective circuit board on which a protection circuit is mounted to prevent an accident caused by over-charging, over-discharging, over-current, and the like.
In a pouch-type secondary battery, after an electrode assembly formed by winding a positive electrode plate, a negative electrode plate, and a separator is sealed in the pouch-type case, the secondary battery is connected to the protective circuit board.
Then, a positive electrode tab connected to the positive electrode plate and a negative electrode tab connected to the negative electrode plate, both tabs protruding outward from one side of the pouch-type case, are connected to their corresponding electrical terminals of the protective circuit board, typically using lead plates.
In general, methods, such as ultrasonic welding, resistance welding, laser welding and the like, are used to connect the lead plate to the electrode tab. However, in the laser welding method, the equipment is expensive and difficult to maintain because replacement components are also expensive. In the resistance welding method, its use range is narrow and it is difficult to be applied to an aluminum material. Moreover, the reliability of a welded part is low after the resistance welding is performed. Further, in the ultrasonic welding, its quality variation is large, and a protection circuit module is likely to be damaged by ultrasonic vibrations generated during the welding process.